Chapters 1 to 6
Chapters 7 to 12
Transport in Plant
Chapters 13 to 17
Chapters 18 to 22
11 Bio Chapter Summary
Photosynthesis is a process in which the plants use light energy to make carbohydrate from carbon dioxide and water.
Photosynthesis occurs in two stages, viz.
. The light reaction is light-dependent.
Dark reaction is
reaction. Dark reaction is utilised to capture and reduce carbon dioxide. Dark reaction doesn’t mean that it happens in the absence of light.
Chloroplast is the cell organelle where photosynthesis takes place in plants and algae. A typical plant cell may contain about 10 to 100 chloroplasts.
Chlorophyll is the main pigment to absorb light. Additionally, carotenes and xanthophylls are also used by plants to absorb light energy. Algae also use chlorophyll for absorbing light.
is also called the
. It includes light absorption, water splitting, oxygen release and the formation of high-energy chemical intermediates (ATP and NADPH). Many complexes are involved in the process.
Water is split into H
, [O] and electrons. The
splitting of water
is associated with PS II. This creates oxygen.
provides replacement for electrons removed from PS I.
Synthesis of ATP from ADP and inorganic phosphate in the presence of light is called
When the two photosystems work in a series; first PS II and then the PS I; a process called
When only PS I is functional, the electron is circulated within the photosystem and the cyclic flow of electrons leads to phosphorylation.
The products of light reaction are ATP, NADPH and O
can be described under three stages:
carboxylation, reduction and regeneration
Fixation of CO
into a stable organic intermediate is called
. In this step, carbon dioxide is utilised for the carboxylation of RuBP.
Reduction involves utilization of 2 molecules of ATP for phosphorylation and two of NADPH for reduction of each CO
molecule fixed. For the removal of one molecule of glucose from the pathway, fixation of six molecules of CO
and 6 turns of the cycle are required.
Regeneration involves regeneration of CO
acceptor molecule RuBP. This is necessary for the cycle to continue without interruption. This step requires one ATP for phosphorylation to form RuBP.
Thus, for each CO
molecule entering the Calvin Cycle, 3 molecules of ATP and 2 of NADPH are required.
Plants which are adapted to dry tropical regions use the
is the first carbon fixation product in C3 plants, it is
(4 carbon atoms) which is the first carbon fixation product in C4 plants.
In C4 plants, large cells are found around the vascular bundles. These are called sheath cells. Leaves have special anatomy; called
is the most abundant enzyme in the world. Its active site can bind to both CO
. But RuBisCO has a much greater affinity for CO
. The relative concentration of O
determines which of them will bind to the enzyme.
Factors which affect photosynthesis are; light, carbon dioxide, temperature and water.
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